[1] The paper presents a summary of more than 4 years of continuous Schumann resonance (SR) monitoring of the vertical electric component at Modra Observatory. Principal parameters (peak frequency, amplitude, and quality factor) are determined for four resonances from 7 to 30 Hz, i.e., for modes one through four. Attention is also given to the less frequently compiled mode four. The resonance parameters are computed from 48 daily measurements and are represented as the mean monthly values for each time of the detection. Fitting of spectral peaks by Lorentz function is the main method used in data postprocessing. Diurnal, seasonal variations and the indication of interannual variations of these parameters (especially peak frequency) are discussed. The results are compared with other observatory measurements. Our observations confirm that variations in peak frequency of the lower-SR modes can be attributed mainly to the source-observer distance effect.

No abstract

No abstract

The electromagnetic eigenmodes of Earth-ionosphere global resonator known as Schumann Resonances (SR) are excited by global lightning activity. The simultaneous measurements of electric field in the ELF (~5 -100 Hz) frequency band at two observatories clearly reveal the global character of the resonator response to the excitation both in the permanent Schumann background as well as in isolated events (transients). It is shown that measurement of ELF electric field can be done with relatively simple equipment.

The cavitational destruction of a thin layer of varnish put on a glass plate was studied by means of high speed photography at the rate of 2000 frames per second. Experiments were carried on in an inactive liquid (water) at the frequency 8000 cps. It was found that the destruction of the film is caused at least by two different factors. Primarily, it is observed as the result of big cavitation bubble collapes in the immediate vicinity of the surface. The obseravation of such bubbles indicates large amplitudes and complex forms of vibration. It is important to note that the process itself of bubble formation and its oscillations at the very surface of the film are without influence on the film; but the bubble collapse leads in the first 1/2000 sec to destruction of the film extending on a circle with the center coinciding with the position of the bubble at the moment of collapse. Another type of destruction is caused by small bubbles with smooth surfaces which quickly penetrate between the film and the glass at a destroyed spot, causing small irregular bits of film to detach from the surface.